Green’s Dictionary of Slang

any powdered drug, e.g. cocaine, heroin.

1949		Monteleone Criminal Sl. (rev. edn).
1953		Anslinger & Tompkins Traffic In Narcotics 307: Old Lady White. Drugs, especially cocaine, heroin, or morphine.
1959		J.E. Schmidt Narcotics Lingo and Lore.